Preheat oven to 400°F (200°C).
In a large skillet, cook Italian sausage, onion, and bell peppers over medium heat until sausage is browned and vegetables are tender. Drain any excess grease.
Stir in garlic, diced tomatoes, tomato sauce, oregano, basil, salt, and pepper. Simmer for 10 minutes.
Press pizza dough into the bottom and up the sides of a 9-inch pie dish.
Spoon the sausage mixture into the dough-lined dish.
Bake for 20 minutes.
Sprinkle mozzarella cheese over the top and bake for an additional 10 minutes or until cheese is melted and bubbly.
Let stand for 5 minutes before slicing and serving.